1. Field of the Invention:
This invention relates generally to safety apparatus and in particular to such protective devices for commercial and residential electric ranges or stoves.
2. Description of Related Art:
The following art defines the present state of this field:
Naugle, U.S. Pat. No. 4,255,669 describes a sensing apparatus for monitoring the operation of an electrical appliance. The sensing apparatus is plugged into a standard electrical outlet and the appliance to be monitored is plugged into the sensing apparatus. The appliance current flows through a transformer in the sensing apparatus. Detection circuitry including a comparator produces one signal when current flow through the transformer is negligible (appliance off) and another signal when the current flow through the transformer is significant (appliance on). Transistor circuitry connected to the detection circuitry produces a pulse at one output terminal on a transition from the one signal to the other signal from the detection circuitry (appliance turned on) and produces a pulse at another output terminal on a transition from the other signal to the one signal from the detection circuitry (appliance turned off).
Nashawaty, U.S. Pat. No. 4,446,455 describes an alarm system for use in a stove having a burner and control device for turning on and off the burner, including an audio/visual alarm device and an alarm circuit for activating the alarm device. A low-voltage power supply energizes the alarm circuit. A sensor is mounted with the burner for sensing the presence and absence of a utensil thereon. A first switch in the alarm circuit closes a first set of contacts in response to the control device being in the burner-on position. A second switch in the alarm circuit closes a second set of contacts in the absence of a utensil on the burner, thereby completing the alarm circuit and activating the audio/visual alarm device.
Lipscher et al., U.S. Pat. No. 4,577,181 describes an alarm system for an electric range which detects when a burner is energized without a utensil in place on the burner wherein the sensing means comprises an electrical switch mounted below the stovetop having a first switch position and a second switch position, a pin slidably passing through an opening in the stovetop beneath the rim of the dish under the heating element in contact with the underside of the rim and biased against the rim with a pressure sufficient to lift the rim from the stovetop when no utensil is present on the heating element, but insufficient to lift the rim when a utensil is in place on the heating element; and means connecting said pin with the switch to operate the switch between first and second positions corresponding to the position of the pin when a utensil is present or absent from the heating element.
Ekblad, U.S. Pat. No. 4,775,913 describes a control device for controlling the operation of an object of cooking such as a stove or the like. The presence of a user in the area of the stove is detected. When the user is present, the stove operation is enabled. After the user has been absent from the area for a first predetermined time, the stove is temporarily disabled, an again enabled when the user enters the area. If the user is absent from the area of the stove for a second predetermined time, the stove is permanently disabled, so that it cannot again be enabled until manually reset.
Sciscoe, U.S. Pat. No. 4,866,427 describes a temperature alarm for attachment around the exterior of the flue pipe of a wood-burning or similar stove, with alarm activation temperature selected by slidable adjustment along the flue pipe. A bimetal thermostat is mounted in close proximity to the flue pipe, and acts to close an electrical connection between thermally protected power supply and acoustic horn. A system test circuit is provided.
Ljunggren, U.S. Pat. No. 5,073,701 describes an arrangement in a range, a cooking hob or the like having at least one electrically heated hot plate and/or oven, comprising a manually operable setting system for the setting of a desired power or temperature for the hot plate or the oven. A detecting system is arranged to detect changes in the setting of the setting system. A timing system co-operates with the detecting system to be activated by the latter. A switching system co-operates with the timing system to disconnect the power to the hot plate or the oven on the reaching of an end time determined by the timing system, said timing system being reset each time the detecting system is activated and then operated to start counting towards the predetermined end time.
McLean et al., U.S. Pat. No. 5,608,378 describes a fire-preventing warning system for alerting an occupant leaving the premises that a stove burner is on, includes (a) a sensor to detect whether a gas or electric stove is “on”, connected to (b) a warning indicator located by the exit door. If the stove burner is on, the warning indicator will light up, or, in the alternative, emit an audible warning, or both, as the door is opened. The sensor and the indicator circuitry may be connected by electrical conductors or by radio frequency transmission; the system may be battery-operated or powered from household current.
Neil, U.S. Pat. No. 5,608,383 describes an automatic temperature alarm system for alerting an operator of a heated apparatus that the apparatus has been heated and untouched for an excessive period of time. In a particular embodiment, the invention comprises a temperature sensor affixed to the heated apparatus that senses its temperature; a vibration sensor that senses motion of the apparatus; a horn to alert the operator; and a system control intelligence in communication with the temperature and vibration sensors and horn for setting an alarm timer to measure an alarm period in response to sensed temperatures and motions and for activating the horn upon expiration of the alarm period. In use of the automatic temperature alarm system, the system control intelligence is operated so that whenever the temperature sensor senses an increase beyond a specific high or trigger temperature, such as a heating temperature of an outdoor barbecue, the system control intelligence sets its alarm timer to commence measurement of the alarm period of time, and upon the expiration of the alarm period of time, for example twenty minutes, the system control intelligence activates the horn. If the system control intelligence senses a motion of the apparatus from the vibration sensor during the alarm period of time, however, it re-sets its alarm timer to re-commence measurement of the alarm period of time. If the horn has been activated, the system control intelligence inactivates it upon sensing any apparatus motion from the vibration sensor.
Clizbe, U.S. Pat. No. 5,693,245 describes an integral electric range surface burner control switch user interface made up of two components. The first component, which controls the burner temperature setting, is a standard knob which is rotated to turn the burner on, as well as set the desired temperature of the particular surface burner. The second component is a timer control ring integrally mounted around the surface burner temperature control knob. The timer control ring is concentric with and has the same central axis as the surface burner temperature control knob, and is rotatable to set the desired cooking time for the particular surface burner. When the selected amount of time expires, the power to the surface burner element is automatically disconnected and the surface burner is disabled, thus requiring a resetting of the timer for further use.
Vaillancourt, U.S. Pat. No. 5,717,188 describes a safety device for electric stoves and ovens wherein there is provided a sensor for sensing when the stove is heating at a certain rate which could constitute a safety hazard and a sensing means for detecting the presence of a person within a predetermined area proximate the stove. When a certain period of time passes without motion by a person in the predetermined area while the stove is in the predetermined operating condition, power to the stove can be reduced.
Devries et al., U.S. Pat. No. 5,939,992 describes a safety apparatus for electric appliances which includes a sensor for sensing that an electric appliance is operating. An alarm coupled with the sensor, whereby an alarm is initiated. A manually operated alarm disabling switch permitting a person supervising the operation of the electric appliance to temporarily disable the alarm for a predetermined time interval.
Cheng, et al. U.S. Pat. No. 5,945,017 describes an electric or gas burner that can be improved by the installation of an automated fire safety device that first determines whether the burner is being attended to and if not, senses the temperature of the cooking utensil on it and automatically shuts off the flow of electricity or gas to the burner when the temperature of the cooking utensil begins to exceed a predetermined temperature range. A motion detector is integrated into the safety device and serves as the front-end to a temperature sensor switch. The switch is designed to trigger a power shut-off mechanism when high utensil temperature is encountered. The mechanism will be deactivated if motion is detected within a set periphery of the stove appliance. It will automatically be reactivated a set time later after no motion is detected. This invention will not interfere with normal cooking procedures while drastically reducing the possibility of kitchen fires due to cooking.
Rak, U.S. Pat. No. 6,130,413 describes a safety device for use in conjunction with an electric cooking stove including a relay unit having a plug having two live pins and a neutral pin for insertion in a stove receptacle, a receptacle receiving a similar plug of a stove, a relay arrangement for interrupting connections between the live pins of the plug, and corresponding live sockets of the receptacle; and a control unit connected to the relay arrangements, the control unit generating signals to activate said relay arrangement; the relay arrangement is configured to interrupt only one at a time of the connections between the live pins and the live sockets, and the relay arrangement further includes preset switch or jumper to select which of said connections is interrupted. The control unit preferably includes a device to detect the presence of a person in the vicinity of the stove and a timer which restarts a count-down whenever the detection a device fails to detect a person, and causes the control unit to send a signal to the relay arrangements on completing the countdown.
Aldridge et al., U.S. Pat. No. 6,140,620 describes a device for disconnecting an electric appliance or a component thereof from a source of electricity including a circuit connecting the appliance or component thereof to a power source through a relay or other component to open the circuit; and a timer circuit connected to the relay. The timer circuit includes a processor for setting the timer circuit, and a manually operated switch in communication with the processor. The timer circuit is activated for a predetermined time increment by closing the switch, and the relay is closed while the timer circuit is activated. When the switch is closed again while the timer circuit is activated, an additional time increment is added to the activation period.
Hoellerich, U.S. Pat. No. 6,294,994 describes an attendance monitoring apparatus for an appliance, such as an electrical appliance, and includes a housing and a motion sensor assembly contained in the housing. A timer assembly is electrically connected to the motion sensor assembly, and an alarm assembly is electrically connected to the timer assembly. The timer assembly is adjustable for selecting a range of predetermined time intervals. Optionally, a current controller is electrically connected to the timer assembly. The current controller controls electric power to the appliance, such as an electric stove. The attendance monitoring apparatus of the invention signals a person with an audible alarm when the person has not attended to the electric stove for a predetermined period of time. Optionally, the attendance monitoring apparatus can turn off electrical power to the stove under these conditions. In this way, the attendance monitoring apparatus of the invention increases an operator's freedom and electric stove safety when the stove is in use. As a result, the attendance monitoring apparatus can prevent fires and save lives.
Campbell, U.S. Pat. No. 6,420,969 describes a system for arming and disarming a central intrusion alarm system control utilizing the activation status of a particular appliance. The system employs a detector for determining the position of an on-off switch associated with a particular appliance. The regulator prevents the operation of the arming control in a central intrusion alarm system when the detector determines that the appliance is “on”. The system of the present invention may be employed with multiple appliance switches. In addition, transmission of the disarming signal to the central intrusion alarm arming control may be accomplished through hard wires or by radio transmission.
Our prior art search with abstracts described above teaches: a safety apparatus for electric appliances, a sensing apparatus, an appliance alarm system, an appliance attendance monitoring apparatus, an appliance timer, a safety device for electric stoves, a fire safety device for stove-top burners, a safety device for a heating appliance, an electric range temperature control with mandatory timer, an automatic temperature alarm system, an electric stove warning system, an arrangement in a range or cooking hob with temperature control, timer, detector and switching system, a temperature alarm, a safety shutoff device for a stove, an alarm system for an electric range, and a stove alarm system, but does not teach a retrofitted apparatus capable of continuous alarm notice of burner activity with both audio and visual features. The present invention fulfills these needs and provides further related advantages as described in the following summary.